Past research has indicated that young children have a propensity to adopt the causally unnecessary actions of an adult, a phenomenon known as overimitation. Among competing perspectives, social accounts suggest that overimitation satisfies social motivations, be they affiliative or normative, whereas the “copy-all/refine-later” account proposes that overimitation serves a functional purpose by giving children the greatest opportunity to acquire knowledge with little error. Until recently, these two accounts have been difficult to extricate experimentally, but the development of humanoid robots provides a novel test. Here we document that children overimitate robots, but to a lesser degree than humans and regardless of whether the redundant actions are seen to be ritualistic or functional. These results are best explained with a combined account of overimitation, whereby children approach a learning task with a copy-all/refine-later motivation, but the fidelity of the reproduction of novel behaviors is modulated by the social availability of the demonstrator.